Apparatus for determining the lubricating values of oils



F. RAY

March 26,A 1940.

APPARATUS FOR DETERMINIG THE LUBRICATING VALUES OF OILS Filed July 5,1929 3 Sheets-Sheet l March 26, 1940. v F, RAY 2,194,527 v APPARATUS FORDETERMINING THE LUBRICATING VALUES OF OILS Filed July 5, 1929 3Sheets-Sheet 2 ATTORNEYS F. RAY

vMarch 26, 1940.

APPARATUS FOR DETERMINING THE LUBRICATING VALUES-"OF OILS Filed July 5,1929 5 Sheets-Sheet 3 INVENTOR Patented Mar. 26, 1940 UNITEDl STATESAPPARATUS Fon DETERMINING 'rnE LUmoA'rme vALUEs or ons Frederick Ray,short mns, N. J.,

Automatic Appliance assignor to The Company, St. Louis, Mo.,

, a corporationof Missouri Application July s, 192e, 'serial No. 376,041

3 Claims.

This invention is' directed to a novel apparatus for determining thelubricating values of oils as they are used, for example, in automotiveengines and the like.

As is well known, the bearings and cylinders of automotive engines arelubricated by a combined pressure and splash system which circulates thelubricant round and round for use over and over again until it loses itslubricating value. The most commonly employed lubricant is mineral oil,Awhich is readily miscible with the lighter hydrocarbon fuels,- such asgasolinel and kerosene. These lighter fuels are not always completelyconsumed in the operation of the engines, but instead, some of the fuelcollects on the relatively cold cylinder walls and subsequently nnds itswayy past the pistons into the crank case, where it becomes mixed withthe lubricating oil. As a result, the lubricant gradually becomesdiluted, with a consequent reduction in viscosity for lubricating value.f V

Of course, the absolute effect of dilution-upon viscosity is dependentupon the original viscosity, percentage of dilution, and operatingtemperatures, and varies widely under different conditions. In someinstances, for example, such as occur in ordinary practice, a`dilutionofvfrom 10% to 20% will reduce the viscosity of the mixture to about onethird of the viscosity of the pure oil. The various lubricatingoils'used in automotive engines differ widely in viscosity at any giventemperature, and the viscosities of all the different oils vary widelywith the temperature. These oils are subjected to mean temperatures, inthe crank case, of from below 0 F. in Winter to 150 F. or more insummer, and such variations in operating temperatures, with resultantvariations in the vaporization and .condensation of thefuel, producesubstantial varia. tions in the rate of dilution. Furthermore, thesetttingof the carburetor, the improper use of the choke, and themechanical 4condition of the engineparticularly the t of the 'pistonrings in the cylindersT-as well as' the manner of use of the en gine,each contribute in varying degrees to the diluting tendency.

In order to maintain bricant above a certain critical value, it has beencustomary lto use an oil having a greater viscosity than is actuallynecessary, and then to drainthe crank case and replenish with fresh oilat the4 end of every ve hundred or onethousand miles of travel. But froma consideration of the abovementioned variable factors that affect thevis.- cosity of the oil, it is evident that the'rate of various devicesfor heating thelubricating oil` todrive 01T, by distillation,vthe morevolatile gasoline or kerosene as soon as it is mixed with the oil. Suchdevices, aside from being complicated andA cumbersome, aredisadvantageous in -that the additional heating of the oil tends tobreak it down by increasing the rate of carbonization. Furthermore,there is no way for the operator to know whether the device isfunctioning or not, and in the event that it should cease to functionover a distance of two thousand miles, serious damage might result tothe engine.v Other manufacturers have provided their engine crank caseswith Ventilating means to carry oif any vapors 'of the diluting gasolineor kerosene, but devices of this sort are far from being elcient, andthe operator is left totally in the dark.

'I'he foregoing and other objectionable features of the prior art areovercome by thepresent invention, which has for its object the provisionof a novel apparatus for determining andindicating at all timesvariations in the lubricating properties of the oil in an automotiveengine or motor while in operation.

In its broader aspects, the invention contemplates the determination ofthe lubricating prop- "erties of the oil by the translation of someother property. 'or condition into terms of viscosity.

More specifically, the method involved consists in passing a relativelysmall amount of the oil through a circulating system and creatingtherein a pressure which is a function of the viscosity of the oil.Variations in said pressure are measured by a suitable gauge or the likewhich may be calibrated to give an exact indication ofthe viscosity.'I'hecirculatng system is preferably auxiliary to the regularlubricating system of the motor (being in the nature of'a by-pass incircuit therewith) and is provided at one point with. a pressureregulator which maintains a constant the viscosityof the lu pressurelonl the oil'at that point in the system and receives the oil from theusual pump thereof. From this point of constant' pressure, the oil iscaused to flow successively-through a small bore capillary tube and acapillary orifice, one leading to and the other from a common pressurechamber. Since the oil `in flowingl through the tube and the orifice isobedient to diierent laws of flow, there will be created in the commonchamcosity of the oil. It is this pressure which is utilized inoperating the indicator, and consequently' any change of pressure dueto' a changel of viscosity will be immediately registered by theindicator. In this way, the operator is advised at all times as to theviscosity of the oil and will know exactly when it has lost itslubricating value and needs replenishing. So long as the indicator showsthe oil to possess the requisite viscosity under proper operatingconditions, it

may be safely used as a lubricant without regardv to actual mileage orperiod of use of the engine.

The foregoing and other objects, features, and advantages of theinvention will more readily appear from the following description inconnection with the accompaning drawings, wherein the invention has beenshown by way of illustration, and wherein:

Fig. 1 is a perspective view, partly broken away, showing one form oftheinvention as applied to an automobile;

Fig. 2 is a vertical longitudinal sectional view through one form of theimproved viscometer, and showing the indicating gauge associatedtherewith;

Fig. 3 is a side elevation of the viscometer; and

Fig. 4 is a top plan view thereof, partly broken away.

In Fig. 1, one form of apparatus has been shown as applied to anautomobile, but it is to be understood that the invention is notrestricted to such use, but may be employed with equal advantage inother automotive engines, such as for aviation and marine use, and infact in lubricating systems of machines other than gas engines.

The apparatus comprises a viscometer I connected in a closed circulatingsystem at one side of the engine 2, said system including an oil pump 3of any ordinary or preferred type. The pump 3 draws oil from -a sump atthe bottom of the engine crank case through a suction pipe 4, and forcessaid oil through a supply pipe 5 leading to the engine bearings. Thepump 3 and pipes 4 and 5 are parts of the usual pressure lubricatingsystem employed in automobiles, and this system is so well known as torequire no further description.

The viscometer- I is connected to the supply pipe 5 by mean of a branchof a T 6, so that a small portion of the oil from the pump 3 is bypassedthrough the viscometer I and subsequently returned to the oil sumpthrough discharge pipe 1. The oil passing through the viscometer I iscaused to iiow in such manner as to create a pressure which varies(inversely) with the viscosity of the oil, and variations in s'uchpressure are adapted to be' registered by an indicator or gauge 8 on thedashboard of the vehicle, said gauge being connected with the viscometerby means of a pipe or tube 9.

Referring particularly to Figs. 2, 3, and 4, it will be seen that theviscometer unit I comprises a relatively shallow circular body portionI0 and a oil receiving chamber within which a constant pressureis'maintained on theoil by a Pressure regulator I3.

'I'his pressurey regulator comprises a flexible corrugated diaphragm I4,which formsthe upper wall of the pressure chamber I2, having a ceutralreinforcement I5 against which the lower end of a compression spring I6bears. The spring I6 is confined withi a chamber I1 of a housing I8,which is secured, as by screw threads I9, to the body portion I0. Thediaphragm I4 may preferably be soldered to an annular shoulder 20 on thebody portion I0, or it may be clamped "in position between said bodyportion and the housing I8. The upper en'd of the spring I6 `bearsagainst the shouldered inner end 2l .of an adjustable screw plug 22 inthe upper end of the housing I8, and by turning said screw plug. thepressure ofthe spring against the diaphragm may be varied as desired.-The screw plug 22 is formed with a central bore 23 fora purpose to beexplained hereinafter, and is locked in adjusted position by a screw cap24.

In the center of the bottom wall of the chamber I 2, there is a flaredopening 26 through which oil is adapted to ow into said chamber from alongitudinal bore 21 or passage in a downwardly extending boss 28 of thebody portion I0. Disposed within the bore 21, below the opening 26, is

an oil strainer 29 of any desired construction, this strainer beingclamped in the end of the bore 21 by means of a bushing 30, which inturn is held in place by a coupling nut 3l. The bushing 30 is secured toa nipple 32-.which branches out from seat tightly against the annularvalve seat 38 surrounding the lower end of the opening 28. Normally, thepressure of the spring I 6, in acting upon the diaphragm I4, maintainsthe valve 35 in its open position, but ii the pressure of the oil'within the chamber I2 should rise beyond a predetermined amount, thediaphragm will yield upwardly, drawing the valve stem 31 with it andcausing the valve disc to approach the valve seat 38 and reduce the flowof the 'oil through the opening 28, therebyl maintaining a givenconstant pressure within the chamber I2.

In order to adjust thevalve with reference tol the valve seat, andthereby to4 vary the extent of its movement, the lower end of the valvestem` 31 is provided with a head portion having a screwdriver slot 39.Thus, when the body portion ofthe viscometer is disconnected from thecirculating system, a screw-driver may be inserted in the bore 21 toturn the stem 31 in the reinforcing member I5. The stem is soproportioned that its threaded end extends beyond the upper side of thereinforcing member I5 for the reception of a lock nut 40, which may beloosened or tightened as desired by means of a socket wrench insertedthrough the bore 23 of the plug 22.

To providean outlet for the oil from the chamber I2, a coiled small boreor capillary tube 43 is embedded in the body portion I0, as best shownin Figs. 2 and 4. This tube 43'has its inlet end 44 extending upwardlyinto the chamber I2 and its outlet end 45 extending into a longitudinalbore or chamber 46' formed in the cylindrical exu of the cylindricalportion II, and in communication with the bore or chamber 46 therein, isa nozzle member 41 having at its lower end an annular wall 48 formedwith a capillary orifice 49 which preferably is slightly larger than themesh of the strainer 29 and which causes a turbulent ow. The wall 48 istapered or flared both above and below the orifice to produce a sharpedge orifice, which is a type of orifice best suited for the presentinstrument. The orifice 49 discharges into the upper end of the returnpipe 1,which may be secured to the lower end of the rcylindrical portionII by any ordinary or preferred form of coupling or union 50. A venttube I, which is open at its upper end, is connected with the pipe 1 tomaintain atmospheric pressure below the` orifice 49, altho a small ventcut through the pipe 1 would answer the purpose equally well.

In the prior art liquids have been passed through relatively largeorifices to determine their viscosity, the use of such orifices in allinstances being based upon the fact that the pressure drop causing theflow was substantially independent of the viscosity and consequentlyvaries as the square of the velocity through the orifice. To

obey this law of flow with liquids of relativelyl high viscosity such aslubricating oils used in automobiles the size of the orifice andpressure -drop must besuch that a large amount of oil passes through theorifice, in fact many times that available in the lubricating system ofan automobile.

I have discovered that when such liquids flow through a small orificethe flow is not independent of viscosity and consequently the pressuredrop causing the flow does not very as the square of the velocity.. Inthe case of such an orifice the f law of flow (which I believe to be anentirely new discovery) is that the pressure multiplied by a factor(which is a function of viscosity but a constant for a given viscosity)is equal to the velocity to the nth power, n` being a continuousfunction of the viscosity. I have found that n varies continuously fromabout 2 in the case of water or liquids of substantially zero viscosityto about 1 in the case of liquids of high viscosity.

As is well known, the pressure drop to cause the flow ofthe liquidthrough a small bore or capillary tube is directly proportional to thevelocity of the liquid. Likewise the pressure 'drop to cause flow isdirectly proportional to the ,viscosity. When n has a value of 2 theflow is substantially free from the effect of viscosity, the

pressure head being entirely transformed into velocity head. When n hasa value of 1 the-ow is entirely viscous, the pressure head beingutilized entirely in overcoming the shearingrhtl ance to flow. Forintermediate values of n part of the pressure head is utilized toovercome shear and part is transformed into velocity head. As aconsequence for all values of n greater than 1 the variation in thepressure drop to 'cause flow" have ascertained that such flowcharacteristics hold for small orifices of minute or pinhole order ofmagnitude. How large the capillary orifice may be made and still producea flow which is dependent on the viscosity is still problematical and Iam not now prepared to give any definite size limitsfor the orificecovering the range over which the lawset forth holds true.

,From the foregoing, it will be clear that any variation in theviscosity of the oil circulated through the instrument will result in achange of pressure within the chamber 46, and hence by a suitablecalibration of the gauge 8, a direct reading in terms of viscosity canbe had. Accordingly, .one end of the tube 9 is connected by a couplingor union 55 with the'upperv end of the cylindrical portion Il, the otherend of said tube 9 extending to the gauge 8, which is located on theinstrument board as previously explained. The gauge 8 may be .ofordinary commercial form having pressure-responsive means, such as aBourdon tube, bellows, or diaphragm, to cause rotation of a pointer 56.The gauge 8 has a graduated dial reading from zero to 2 in acounterclockwise direction, the magnitude of the divisions graduallydecreasing as they approach the value 2. The pointer 56 is shownpointing to the zero mark which corresponds to the maximum pressurewithin the chamber 46, which condition would result from the passagethrough the viscometer of a fluid having zero viscosity. This is anideal condition which does not exist in reality, but which is closelyapproximated with Water.

, Under conditions of atmospheric pressure in the strument from thechamber I2 to the pipe 1 is constant, and since the same quantity ofliquid flows through the capillary tube 43 and capillary orifice 49, itfollows that the proportional distribution of this drop in the tube andorifice will vary as the viscosity varies. In consequence, the pressure.in the -chamber 46 relative to the atmosphere will vary, and thisvariation will be indicated by the gauge 8 connected thereto.

The proportions of the tube 43 and orifice 49 may be varied withinreasonable limits and in accordance with requirements of design forparticular instruments. By way of illustration, satisfactory resultshave been lobtainedwith the device shown in the drawings, wherein theorifice 49 is about .035 inch in diameter, and the tube 43 is about sa;inch in inside diameter and aboutk 5 inches in total length. Thepressure main-9 tained within .the chamber I2 by the regulator I3 may beabout three pounds to the squareinch, the spring I6 being adjustablemerely to suit the calibrations of the gauge 8.

The relative arrangement of thesmall bore tube 43 and capillary orifice49 can be reversed if desired but I prefer the first-disclosed ar.rangement wherein the oil rst flows through the tube and then throughthe orifice. As has previously been stated, with this preferredarrangement the pressure in the chamber 48 will varyl inversely with theviscosity, and this is desirable because it prevents any possible damageto the gauge when the viscosity is high due to low temperatures, as whenstarting the engine in cold weather. In yother words,as the viscositydecreases the pressure in the common chamber^46 increases, and the gaugecan be so selected and calibrated, as to be capable of withstanding themaximum pressure caused by the flow of the change.

least viscous iuids. If the pressure were to vary directly-with theviscosity, it is conceivable that in startingl in cold Weather, the oilmight be so thick as to create a pressure beyond the rangeof the gauge,causing injury to the instrument which would render it inaccurate andundependable in future use.

It will now be apparent that an apparatus has been provided forcontinuously testing, determining, and indicating the viscosity of theoil in an automotive engine while itis in operation, so that theoperator will be advised at all times asto the actual lubricating valueof the oil. When the indication given by the gauge 8 reaches apredetermined minimum -value for that Vparticular engine, he will knowthat the oil requires to be changed irrespective of the distance hemight have travelled sincethe last But until such `indication is given,he will know that the oil is satisfactory for use and need not beWasted. Thus the instrument is 'of great utility in that it saves thtengine when the oil is bad, and it saves the oil when the oil is good. y

Obviously. the invention is susceptible of numerous modifications in theconstruction of the apparatus, and the right vis herein reserved to 1. Aviscometer for determining the viscosity of oil which is subjected todestructive iniiuences aiectingits viscosity, comprising an oilreceiving chamber, a yieldable diaphragm forming one wall of saidchamber, a spring acting on said diaphragm to maintain a constantpressureA within said receiving chamber, a pressure-regulating valveassociated with the diaphragm to control the ilow of oil into thereceiving chamber, a variable pressure chamber adapted to be suppliedwith 'oil from the receiving chamber and provided with a capillaryorifice as an outlet for the oil, means for regulating the outlet pres'-'sure at the orifice so that a constant pressure drop is maintainedbetween the oil receiving itial and final pressures on the `fluidpassing chamber and the outlet of the orice, a small bore capillary tubeof substantial length for conducting the oil from the receiving chamberto said variable pressure chamber, said tube and orice being soproportioned as to cause viscous I ow through the tube and partiallynon-viscous ilow through the oriflce so asto create within the pressurechamber a pressure which is dependent upon the viscosity oi.' the oil,and means for indicating variations in said pressure in l0 terms ofviscosity. y

2. A viscometerl of `the class described, comprising a casing having ashallow oil receiving chamber, a diaphragm forming a yieldable wall forsaid chamber, a self-alining valve associated lwith the 'diaphragm tocontrol the ilow of oil f into saidreceiving chamber, -a compressionspring acting against the diaphragm to maintaina substantially constantpressure in the receiving chamber, a line-mesh strainer through whichoil isA caused to flow before entering said chamber, a'variable pressurechamber at one side of the receiving chamber, a. nozzle in the bottom ofsaid variable pressure chamber and provided with an outlet oriceslightly larger than the mesh of said strainer, -said orice leading intoa conduit having an atmospheric vent, a'small bore tube for conductingthe. oil from the receiving chamber to said variable pressure chamber,said tubeintermediate its ends being coiled beneath l the receivingchamber, and said tube and orifice being sotproportioned as to createwithin the pressure chamber, a pressure which is a, function of thelviscosity of the oil, andan indicator responsive to the variationsinpressure'in the 35 pressure chamber to indicate variations in viscosity.l

3. Apparatus for continuously indicating 'the viscosity oi a iiuid,which comprisesa variablepressure chamber, a capillary tube providing aninlet to said chamber,- a capillary orifice providing an outlet from'said' chamber, said capillary tube causing stream line ilow and theorifice causing turbulent iiow of the uid passing therethrough, meansfor maintaining substantially constant inthrough the apparatusirrespective of any change which may occui' in the fluid, and means formeasuring pressure in said chamber to give an indication of theviscosity of the fluid at any time..4

' FREDERICK RAY.

